Electro-optic liquid sensor with the use of reflected residual light to enable a test of the sensor

ABSTRACT

A method of operating an electro-optic sensor includes disposing at least a portion of the electro-optic sensor in a liquid chamber, providing light from a light source of the electro-optic sensor at a first intensity, driving a light detector of the electro-optic sensor at a first sensitivity level, receiving, via the light detector, a first amount of light from the light source; determining whether liquid is present in the liquid chamber according to the first amount of light, providing light from the light source at a second intensity, driving the light detector at a second sensitivity level, receiving, via the light detector, a second amount of light from the light source, and/or confirming whether liquid is present in the liquid chamber according to the second amount of light. The first sensitivity level may be different from the second sensitivity level.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 14/912,747 filed Feb. 18, 2016, which is a national phaseapplication of PCT Application PCT/US2014/054696 filed Sep. 9, 2014,which claims the benefit of U.S. Provisional Patent Application Ser. No.61/875,892 filed Sep. 10, 2013, the disclosures of which are herebyincorporated herein by reference in their entireties. This applicationclaims the benefit of U.S. Provisional Patent Application Ser. No.62/419,240, filed on Nov. 8, 2016, the disclosure of which is herebyincorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to liquid sensors, includingelectro-optic liquid sensors.

BACKGROUND

This background description is set forth below for the purpose ofproviding context only. Therefore, any aspects of this backgrounddescription, to the extent that it does not otherwise qualify as priorart, is neither expressly nor impliedly admitted as prior art againstthe instant disclosure.

Numerous components in numerous different fields are dependent on thepresence or absence of liquid, or a certain amount of liquid.Accordingly, sensors have been developed for detecting the presence offluid. One sensor type is an electro-optic sensor including a lightsource, a prism, and a light detector.

In electro-optic liquid sensors, light emitted from the light source maybe returned to the light detector by the prism only if no liquid ispresent. If liquid is present, no light or limited light may be returnedto the light detector.

There is a desire for solutions/options that minimize or eliminate oneor more challenges or shortcomings of electro-optic sensors. Theforegoing discussion is intended only to illustrate examples of thepresent field and should not be taken as a disavowal of scope.

SUMMARY

In embodiments, a method of operating an electro-optic sensor mayinclude disposing at least a portion of the electro-optic sensor in aliquid chamber; providing light from a light source of the electro-opticsensor at a first intensity; driving a light detector of theelectro-optic sensor at a first sensitivity level; receiving, via thelight detector, a first amount of light from the light source;determining whether liquid is present in the liquid chamber according tothe first amount of light; providing light from the light source at asecond intensity; driving the light detector at a second sensitivitylevel; receiving, via the light detector, a second amount of light fromthe light source; and/or confirming whether liquid is present in theliquid chamber according to the second amount of light. The firstsensitivity level may be different from the second sensitivity level.Determining whether liquid is present in the liquid chamber according tothe first amount of light may include comparing the first amount oflight to a threshold value, determining that liquid is present if thefirst amount of light is greater than the threshold value, and/ordetermining that liquid is not present if the first amount of light isnot greater than the threshold value.

In embodiments, if the first amount of light is greater than thethreshold value, the second intensity may be greater than the firstintensity and the second sensitivity level may be more sensitive thanthe first sensitivity level. Confirming whether liquid is present in theliquid chamber may include confirming that liquid is present if thesecond amount of light is greater than a second threshold value anddetermining an error has occurred if the second amount of light is notgreater than the second threshold value.

With embodiments, if the first amount of light is not greater than thethreshold value, the second intensity may be less than the firstintensity and the second sensitivity level may be less sensitive thanthe first sensitivity level (e.g., effectively a third intensity and athird sensitivity). Confirming whether liquid is present in the liquidchamber may include confirming that liquid is not present if the secondamount of light is less than a third threshold value and determining anerror has occurred if the second amount of light is not less than thethird threshold value.

In embodiments, the electro-optic sensor may include a prism and areflective optical member. The reflective optical member may be arrangedto reflect light emitted by the light source to the light detector whena liquid is disposed between the light source and the reflective opticalmember. The light detector may include an optical head assembly disposedin the liquid chamber and an electronic module assembly disposed outsideof the liquid chamber. The optical head assembly is connected to theelectronic module assembly via one or more fiber optic cables. At leastone fiber optic cable of the one or more fiber optic cables may beconnected to a wall of the liquid chamber via a hermetically sealedfitting. The one or more fiber optic cables may include a single fiber.The method may include disposing all active components of theelectro-optic sensor outside of the liquid chamber.

With embodiments, a method of operating an electro-optic sensor mayinclude providing a liquid chamber; providing the electro-optic sensorincluding a light source and a light detector that may include aphotodiode-based transimpedance amplifier; conducting a first test ofthe electro-optic sensor without liquid in the liquid chamber and withthe light source off; conducting a second test of the electro-opticsensor without liquid in the liquid chamber and with the light sourceon; conducting a third test of the electro-optic sensor with liquid inthe liquid chamber and with the light source off; conducting a fourthtest of the electro-optic sensor with liquid in the liquid chamber andwith the light source on; setting a threshold value for theelectro-optic sensor according to results of the fourth test; and/oroperating the electro-optic sensor in a normal operating mode, includingdetermining that liquid is present in the liquid chamber if at least oneof an intensity and an amount of light received by the light detector isless than the threshold value.

In embodiments, an electro-optic sensor may include an electronic moduleassembly; an optical head assembly configured to be disposed in a liquidchamber; and/or a fiber optic cable configured to connect the electronicmodule assembly with the optical head assembly. The fiber optic cablemay include a first section with a first end configured for connectionto the optical head assembly and a second end configured for connectionthrough a wall of the liquid chamber. The fiber optic cable may includea second section with a first end configured for connection with thesecond end of the first section. The second end of the second sectionmay be configured for connection with the electronic module assembly. Anelectro-optic sensor may include a first connector connected to thesecond end of the first section of the fiber optic cable, and a secondconnector connected to the first end of the second section of the fiberoptic cable. The first connector and the second connector may beconfigured to be connected together. An electro-optic sensor may includea third connector connected to the second end of the second section ofthe fiber optic cable. The electronic module assembly may include aconnector configured to be connected with the third connector. At leastone of the first section and the second section may include a singlefiber. An electro-optic sensor may include a light source configured tobe driven at a plurality of intensities. The optical head assembly maybe configured to receive light from the light source.

With embodiments, a fluid system may include an electro-optic sensor.The fluid system may include a liquid chamber. An optical head assemblymay be disposed in the liquid chamber. The electronic module assemblymay be disposed outside the liquid chamber. The first section of thefiber optic cable may be connected to the wall of the liquid chamber.The first section of the fiber optic cable may be connected to the wallvia a hermetically sealed fitting. All active components of theelectro-optic sensor may be disposed outside of the liquid chamber. Thefirst end of the first section of the fiber optic cable may be connectedto the optical head assembly via corresponding connectors.

Liquid sensors according to the present disclosure may improve on otherelectro-optic liquid sensors by providing capability for assessing theoperational state of the sensor in the presence of liquid. In contrast,some electro-optic sensors are generally only capable of being testedwhile not in liquid. Accordingly, electro-optic sensors according to thepresent disclosure may enable improved testing and functionality overother electro-optic liquid sensors.

The foregoing and other aspects, features, details, utilities, and/oradvantages of embodiments of the present disclosure will be apparentfrom reading the following description, and from reviewing theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure will now be described, by way of example,with reference to the accompanying drawings, wherein:

FIG. 1 is a block diagram view of an exemplary embodiment of a systemincluding a component for which determining the presence of fluid may bedesirable.

FIG. 2 is a diagrammatic view of an exemplary embodiment of anelectro-optic liquid sensor.

FIG. 3 is a diagrammatic view of the electro-optic liquid sensor of FIG.2 illustrating the operation of the liquid sensor in the absence ofliquid.

FIG. 4 is a diagrammatic view of the electro-optic liquid sensor of FIG.2 illustrating the operation of the liquid sensor in the presence ofliquid.

FIG. 5 is a flow chart illustrating an embodiment of a method ofoperating an electro-optic liquid sensor.

FIG. 6 is a flow chart illustrating an embodiment of a method ofoperating an electro-optic liquid sensor.

FIG. 7 is a flow chart illustrating an embodiment of a method ofoperating an electro-optic liquid sensor.

FIGS. 8 and 9 are diagrammatic views of exemplary embodiments of lightdetectors.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentdisclosure, examples of which are described herein and illustrated inthe accompanying drawings. While the present disclosure will bedescribed in conjunction with embodiments and/or examples, it will beunderstood that they are not intended to limit the present disclosure tothese embodiments and/or examples. On the contrary, the presentdisclosure is intended to cover alternatives, modifications, andequivalents.

Referring to the figures, in which like reference numerals refer to thesame or similar features in the various views, FIG. 1 is a block diagramview of a system 10 including a component 12 for which determining thepresence of liquid may be desirable. The component 12 may include aliquid chamber 14, and the system 10 may include a liquid sensor 16and/or an electronic control unit (ECU) 18.

In embodiments, the component 12 may be any component in any field thatincludes or may be exposed to liquid in its operation. For example, thecomponent 12 may be or may be included in a mechanical, electrical,hydraulic, pneumatic, and/or other known actuator or actuation system.The component 12 may include a liquid chamber 14 configured to storeand/or receive a liquid. The liquid may be, for example only, of a typenecessary for the functionality of the component 12 (e.g., hydraulicfluid, liquid for lubrication, fuel, etc.), liquid incidental to theenvironment of the component 12, and/or liquid that is detrimental tothe function of the component 12.

With embodiments, the liquid sensor 16 may be coupled with the component12. For example, the liquid sensor 16 may be disposed at least partiallywithin the liquid chamber 14 of the component 12. In embodiments, theliquid sensor 16 may be an electro-optic sensor, such as that describedin conjunction with FIGS. 2-4 and/or FIGS. 8 and 9.

With continued reference to FIG. 1, an ECU 18 may be electricallycoupled to the sensor 16 and may be configured to drive the sensor 16,receive feedback from the sensor 16, assess whether liquid is present orabsent in the liquid chamber 14, and/or assess the operational state ofthe sensor 16. An ECU 18 may comprise, in embodiments, one or more of aprocessor, a non-volatile computer-readable memory, anapplication-specific integrated circuit (ASIC), field-programmable gatearray (FPGA), and/or other known processing or memory devices. The ECU18 may be or may comprise a dedicated processing resource for the sensor16, or may be or may comprise processing resources for numerous sensors,components, and/or systems. The ECU 18 may be electrically coupled tothe sensor 16 through known wired and/or wireless connections. The ECU18 may be configured to perform various functions, including thosedescribed in greater detail herein, with appropriate programminginstructions and/or code embodied in software, hardware, and/or othermedia. In embodiments, the ECU 18 may include a plurality ofcontrollers. In embodiments, the ECU 18 may include and/or be connectedto an input/output (I/O) interface and/or a display.

FIG. 2 is a diagrammatic view of an exemplary embodiment of theelectro-optic liquid sensor 16. The sensor 16 may include a light source20, a light detector 22, a prism 24, and/or a reflective optical member26 (which may also be referred to as an optical shield), which may begenerally disposed within a housing 28. The housing 28 may include oneor more liquid ports 30 for permitting liquid to flow into and out of achamber 32 of the housing 28. The chamber 32 may define a gap betweenthe prism 24 and the optical member 26 of a size d. For example, andwithout limitation, in an embodiment, d may be about an inch or less. Ofcourse, other dimensions may be employed as appropriate for particularapplications.

With embodiments, the light source 20 may be configured to emit light ofone or more chosen frequencies and powers/intensities appropriate for agiven application (e.g., appropriate for the characteristics of theother elements of the sensor 16, such as shape, orientation, materials,reflectivity, etc., and/or according to characteristics of the liquid tobe detected, such as density, scattering properties, etc.). As usedherein, a light frequency should be understood to include either or bothof a specific frequency of light and a frequency band. In an embodiment,the light source 20 may be configured to emit light in the infraredportion and/or the near-infrared portion of the electromagneticspectrum. The light source 20 may be or may include one or more of alight-emitting diode (LED), a laser, or other known light source, in anembodiment.

The light detector 22 may be configured, in an embodiment, to detectlight of one or more frequencies of light, including at least thefrequency of light emitted by the light source 20. The light detector 22may be or may include one or more of a phototransistor, photodiode,and/or other light detecting device.

In embodiments, the prism 24 may include a member, article, and/ordevice comprising one or more components that may be configured in size,shape, and/or materials to reflect light/a light signal from the lightsource 20 to the light detector 22 in certain conditions and to passlight from the light source 20 through the prism 24 in certainconditions. For example only, the prism 24 may be configured to reflectlight from the light source 20 to the light detector 22 when liquid isnot present around the prism 24, and to pass light from the light sourcethrough the prism 24 when liquid is present around and/or near the prism24 (e.g., in chamber 32). In an embodiment, for example only, the prism24 may comprise borosilicate glass, fused silica (quartz), one or morepolymers, etc., that is optically transmissive at least to light of thefrequency or frequencies emitted by the light source 20. Thus, in anembodiment, the prism 24 may be optically-transmissive to light in theinfrared and/or near-infrared portions of the electromagnetic spectrum,for example only.

With embodiments, a reflective optical member 26 may be arranged andconfigured to reflect light emitted by the light source 20 to the lightdetector 22, in certain conditions. The optical member 26 may have adegree of reflectivity for one or more frequencies of light that may betailored for a particular application. In certain embodiments, theoptical member 26 may have complete or near-complete reflectivity forthe frequency or frequencies of light emitted by the light source 20. Inother embodiments, the optical member 26 may have less-than-completereflectivity for the frequency or frequencies of light emitted by thelight source 20.

The reflective optical member 26 may be disposed, in an embodiment,on/at a side of the housing 28 opposite the light source 20 and thelight detector 22. The light source 20 may emit light in the directionof the optical member 26. The prism 24 may be disposed at leastpartially between the light source 20 and the optical member 26, in anembodiment, and at least partially between the light detector 22 and theoptical member 26, in an embodiment. Accordingly, in the embodimentgenerally illustrated in FIG. 2, light may travel from the light source20, through the prism 24, through the chamber 32, to the optical member26, and may be reflected by the optical member 26 back through thechamber 32 and prism 24 to the light detector 22, in certain conditions.The distance d between the optical member 26 and the prism 24 may betailored to the geometric relationship between the optical member 26,prism 24, light detector 22, and light source 20, in an embodiment, forthe optical member 26 to effectively reflect light emitted by the lightsource 20 to be returned to the light detector 22.

In embodiments, the electro-optic liquid sensor 16 may be configured todetect the presence of liquid by returning a different amount of lightfrom the light source 20 to the light detector 22 when liquid is presentin the chamber 32 than when liquid is not present in the chamber 32. Forexample, as shown in FIG. 3, when no liquid is present in the chamber32, and the chamber 32 is filled with air, the prism 24 may return afirst amount of light from the light source 20 to the light detector 22.In an embodiment, the prism 24 may return substantially all lightemitted by the light source 20 to the light detector 22 when no liquidis present. In contrast, as shown in FIG. 4, when the chamber 32 isfilled with liquid, the prism 24 may return very little of or none ofthe light from the light source 20 to the light detector 22. The prism24 may pass some portion of the light emitted by the light source 20,some of which light may disperse in the liquid, and some of which lightmay propagate to the optical member 26, be reflected by the opticalmember 26 to the light detector 22, and be received by the lightdetector 22. Accordingly, a relatively higher amount of light receivedby the light detector 22 may be associated with the absence of liquidfrom the chamber 32, and a relatively smaller amount of light receivedby the light detector 22 may be associated with the presence of liquidin the chamber 32.

Embodiments of an electro-optic liquid sensor 16 may improve on otherelectro-optic sensors by enabling the sensor 16 to be tested in thepresence of liquid. Other electro-optic sensors generally do not provideany means by which a light signal may be returned to the light detectorin the presence of liquid. As a result, a faulty sensor may beindistinguishable from the presence of liquid in known sensors. Incontrast, because the electro-optic sensor 16 of the present disclosuremay return a light signal to the light detector 22 in the presence ofliquid, a faulty sensor (which may always indicate zero light receivedby the light detector 22) may be distinguished from the presence offluid (which may indicate a nonzero amount of light received by thelight detector, but less light received by the light detector 22 thanwhen liquid is absent).

Although embodiments of the electro-optic liquid sensor 16 are describedherein with respect to particular materials, shapes, dimensions, lightcharacteristics, etc., it should be understood that such details areexemplary only and are not limiting except as explicitly recited in theclaims. Numerous modifications and alterations may be made within thespirit and scope of the present disclosure.

Referring to FIGS. 1 and 2, an ECU 18 may be configured to operate theelectro-optic sensor 16 to determine whether liquid is present in thechamber 32 and to determine whether the sensor 16 is or is not operatingproperly (e.g., assess the operational state of the sensor 16).Accordingly, in an embodiment, the ECU 18 may be configured to operatethe sensor 16 in a liquid detection mode and a test mode. The liquiddetection mode and the test mode may be implemented separately by theECU, or may be implemented together.

FIG. 5 is a flow chart generally illustrating a method 40 of operatingan electro-optic sensor 16. One or more steps of the method 40 may beperformed by the ECU 18 shown in FIG. 1 to operate the sensor 16 of FIG.2. The method 40 may include steps for implementing a liquid detectionmode and a test mode of the electro-optic sensor 16 together.

Referring to FIGS. 2 and 5, an embodiment of a method 40 may begin witha first driving step 42 that includes driving (e.g., providing lightfrom) the light source 20 at a first frequency and intensity. Thefrequency and intensity may be selected according to the characteristicsof the components of the sensor 16 and/or according to the liquid to bedetected. The method 40 may continue to a first receiving step 44 thatmay include receiving reflected light with the light detector 22. Thereceived light may be of the same frequency as that emitted by the lightsource 20 in the first driving step 42. In a first comparison step 46,the amount or intensity or light received, R₁, may be compared to afirst threshold, T₁.

With embodiments, if the amount or intensity of light R₁ detected in thefirst receiving step 44 is less than the first threshold T₁, the method40 may continue to a second driving step 48 that includes driving thelight source 20 at a second frequency and intensity. The secondfrequency may be the same as the first frequency, in an embodiment. Thesecond intensity may be the same as the first intensity, in anembodiment. In another embodiment, the second frequency and/or intensitymay be different from the first frequency and/or intensity. For exampleonly, the second intensity may be greater than the first intensity, inan embodiment. A higher intensity may be used in the second driving step48 than in the first driving step 42 to ensure that, if liquid ispresent, the light will have sufficient energy to propagate through theliquid from the light source 20 to the optical member 26 and back to thelight detector 22. Thus, as in the first driving step 42, the frequencyand intensity of light in the second driving step 48 may be selectedaccording to the type of liquid to be detected and the characteristicsof the elements of the sensor.

In embodiments, the method 40 may continue to a second receiving step 50that includes receiving reflected light with the light detector 22. Thereceived light may be of the same frequency as that emitted by the lightsource 20 in the second driving step 48. In a second comparison step 52,the amount or intensity or light received, R₂, may be compared to asecond threshold, T₂. If the amount or intensity of light received isgreater than the second threshold (e.g., if R₂>T₂), it may be concludedat a first conclusion step 54 that liquid is present and that the sensor16 is functioning properly. If the amount or intensity of light receivedR₂ is not greater than the second threshold T₂, it may be concluded at asecond conclusion step 56 that the sensor 16 is not functioningproperly.

With embodiments, in the first comparison step 46, if the amount orintensity of light received is greater than the first threshold (e.g.,if R₁>T₁), the method 40 may advance to a third driving step 58 that mayinclude driving the light source 20 at a third frequency and intensity.The third frequency may be the same as either or both of the firstfrequency and the second frequency, in an embodiment. The thirdintensity may be the same as either or both of the first intensity andthe second intensity, in an embodiment. In another embodiment, the thirdfrequency and/or intensity may be different from either or both of thefirst and second frequency and/or intensity. The frequency and intensityof light in the third driving step 58 may be selected according to thetype of liquid to be detected and the characteristics of the elements ofthe sensor.

In embodiments, the method 40 may continue to a third receiving step 60that includes receiving reflected light with the light detector 22. Thereceived light may be of the same frequency as that emitted by the lightsource 20 in the third driving step 58. In a third comparison step 62,the amount or intensity or light received, R₃, may be compared to athird threshold, T₃. The third threshold T₃ may be set to an amount orintensity of light that is higher than a properly-functioning sensorcould detect given the amount or intensity of light emitted in the thirddriving step 58. If the amount or intensity of light R₃ received is lessthan the third threshold T₃, it may be concluded at a third conclusionstep 64 that no liquid is present and that the sensor 16 is functioningproperly. If the amount or intensity of light received R₃ is greaterthan the third threshold T₃, it may be concluded again at the secondconclusion step 56 that the sensor 16 is not functioning properly.

With embodiments, the thresholds T₁, T₂, T₃ for determining whetherliquid is present and whether the sensor 16 is functioning properly maybe selected according to the characteristics of the liquid to bedetected and the characteristics of the elements of the sensor 16.Additionally or alternatively, the thresholds T₁, T₂, T₃ may beexperimentally determined.

In embodiments, the steps of the method 40 may be performed repeatedly,in an embodiment, to assess whether liquid is present and whether thesensor 16 is functioning properly on an ongoing basis. That is, acontinuous loop of driving the light source 20, receiving light with thelight detector 22, and comparing the amount or intensity of lightreceived to one or more thresholds may be executed. In an embodiment inwhich the first, second, and third driving steps 42, 48, 58 utilize thesame frequency and intensity of light, the light source 20 may becontinuously driven at a single frequency and intensity.

In an alternate embodiment, the third driving, receiving, and comparingsteps 58, 60, 62 may be omitted and, if the first amount of receivedlight R₁ is greater than the first threshold T₁, it may be concludedthat no liquid is present.

The first driving, receiving, and comparing steps 42, 44, 46 may beconsidered steps in an embodiment of a method of assessing the presenceof liquid (e.g., a liquid detection mode). The second and third driving,receiving, and comparing steps 48, 50, 52, 58, 60, 62 may be consideredsteps in an embodiment of a method of assessing the operational state ofthe sensor (e.g., a testing mode). The liquid presence assessment methodmay be performed separately and independently from the operational stateassessment method, in an embodiment. For example, the operational stateassessment method steps 48, 50, 52, 58, 60, 62 may be performed on aless-frequent basis than the liquid presence assessment steps 42, 44,46, in an embodiment. Furthermore, although methods (e.g., method 40)may be illustrated and described such that operational state assessmentsteps (e.g., steps 48, 50, 52, 58, 60, 62) are only performed afterperforming liquid presence assessment steps (e.g., steps 42, 44, 46),such description and illustration is exemplary only. In an embodiment,the operational state assessment steps 48, 50, 52, 58, 60, 62 may beperformed regardless of performance of the liquid presence assessmentsteps 42, 44, 46.

With embodiments, increasing the intensity of the light source 20 mayinvolve providing a relatively high electrical current to the lightsource 20 and/or creating a temporary current spike in sensor powerconsumption. In some embodiments, the degree to which the intensity oflight from light source 20 can be increased (e.g., via increasingelectrical current) may be limited. For example, and without limitation,there may be limits on available electrical current and/or electricalvoltage, high electrical currents may strain components of sensor 16,and/or other related components may not be fully compatible with highercurrents. In addition to (or as an alternative to) modifying theintensity of the light from the light source 20, with embodiments, thesensitivity level of the light detector 22 may be modified. The lightdetector 22 may include, for example, a photodiode-based transimpedanceamplifier (TIA) receiver, and may be driven at various sensitivitylevels that may correspond with the frequency and/or intensity of lightof the light source 20. A photodiode TIA receiver may be more easilyadjusted than a photo-IC and a photo transistor. Sensor 16 and/or ECU 18may, in at least some circumstances, be configured to operate thephotodiode-based TIA receiver in a linear region.

Referring to FIG. 6, a method 140 of operating an electro-optic sensor16 that includes modifying light intensity and/or detector sensitivitymay include initiating a built-in-test (step 142). The method maycontinue with driving the light source 20 at a first frequency andintensity (step 144). The frequency and intensity may be selectedaccording to the characteristics of the components of the sensor 16 andaccording to the liquid to be detected. The method 140 may includedriving the light detector 22 at a first sensitivity level (step 146).The method 140 may continue to a first receiving step 148 that includesreceiving reflected light R₁ with the light detector 22 with the firstsensitivity level. In a first comparison step 150, the received light R₁may be compared to the first threshold T₁.

In embodiments, if the amount or intensity of light R₁ detected in thefirst receiving step 148 is less than the first threshold T₁, the method140 may continue to a second driving step 160 that includes driving thelight source 20 at a second frequency and intensity. The secondfrequency may be the same as the first frequency, in an embodiment. Thesecond intensity may be the same as the first intensity, in anembodiment. In another embodiment, the second frequency and/or intensitymay be different from the first frequency and/or intensity. For exampleonly, the second intensity may be higher than the first intensity, in anembodiment. A higher intensity may be used in the second driving stepthan in the first driving step to ensure that, if liquid is present, thelight will have sufficient energy to propagate through the liquid fromthe light source 20 to the optical member 26 and back to the lightdetector 22. The method 140 may include driving the light detector 22 ata second sensitivity level that may be the same or similar to the firstsensitivity level (step 162). Additionally or alternatively, the secondsensitivity of the light detector 22 may be modified (e.g., increased),which may help ensure that light is detected. Thus, as in the firstdriving step 144, the frequency and intensity of light and the detectorsensitivity in the second driving steps 160, 162 may be selectedaccording to the type of liquid to be detected and the characteristicsof the elements of the sensor 16.

With embodiments, the method 140 may continue to a second receiving step164 that may include receiving reflected light with the light detector22 with the second sensitivity level. The received light may be ofsubstantially the same frequency as that emitted by the light source 20in the second driving step. In a second comparison step 166, the amountor intensity of light received, R₂, may be compared to the secondthreshold, T₂. If the amount or intensity of light received is greaterthan the second threshold (e.g., if R₂>T₂), it may be concluded at afirst conclusion step 168 that liquid is present and that the sensor 16is functioning properly. If the amount or intensity of light received R₂is not greater than the second threshold T₂, it may be concluded at asecond conclusion step that the sensor 16 is not functioning properly(step 170). Increasing both the intensity of the light and thesensitivity of the detector (e.g., simultaneously) may achieve at leastsimilar functionality/sensing ability and include a smaller increase intotal current than configurations in which only the light intensity isincreased.

With embodiments, in the first comparison step 150, if the amount orintensity of light received is greater than the first threshold (e.g.,if R₁>T₁), the method 140 may advance to a third light driving step 180that may include driving the light source 20 at a third frequency andintensity, and/or a third detector driving step 182 that may includedriving the light detector 22 at a third sensitivity level. The thirdfrequency may or may not be the same as either or both of the firstfrequency and the second frequency, in an embodiment. The thirdintensity may or may not be the same as either or both of the firstintensity and the second intensity, in an embodiment. In anotherembodiment, the third frequency, intensity, and sensitivity level may bedifferent from (e.g., less than) either or both of the first and secondfrequency, intensity, and/or sensitivity. The frequency, intensity, andsensitivity level in the third driving steps 180, 182 may be selectedaccording to the type of liquid to be detected and the characteristicsof the elements of the sensor 16.

In embodiments, the method 140 may continue to a third receiving step184 that includes receiving reflected light with the light detector 22at the third sensitivity level. The received light may be ofsubstantially the same frequency as that emitted by the light source 20in the third driving step. In a third comparison step 186, the amount orintensity of light received, R₃, may be compared to a third threshold,T₃. The third threshold T₃ may be set to an amount or intensity of lightthat is higher than a properly-functioning sensor could detect given theamount or intensity of light emitted in the third driving step. If theamount or intensity of light received R₃ is less than the thirdthreshold T₃, it may be concluded at a third conclusion step 188 that noliquid is present and that the sensor 16 is functioning properly. If theamount or intensity of light received R₃ is greater than the thirdthreshold T₃, it may be concluded at the second conclusion step 170 thatthe sensor 16 is not functioning properly.

Referring to FIG. 7, an embodiment of a method 240 of operating anelectro-optic sensor 16 is generally illustrated. In embodiments, one ormore steps of the method 240 may be used for testing and/or calibrationof the sensor 16 (e.g., a test mode) and one or more steps may be usedfor normal operation (e.g., a liquid detection mode). In a first step242, if the light detector 22 of the electro-optic sensor 16 includes aphoto-IC receiver (or some other type of receiver), a photodiode TIAreceiver may be added and/or used instead. In a second step 244, in theabsence of liquid (e.g., with effectively only air), and with the lightsource 20 off, the light detector 22 may detect a first amount of light(e.g., ambient light). If the first amount of light is above an expectedamount of ambient light, which may be very little or no light, the ECU18 may detect a malfunction, such as with the light detector 22. In athird step 246, the light source 20 may be turned on and the lightdetector 22 may detect a second amount of light (e.g., includingreflected light from the light source 20). If the second amount of lightis below an expected amount of reflected light, the ECU 18 may detect amalfunction, such as, for example, with the light source 20 and/or withthe prism 24. In the third step 246, the electrical current driving thelight source 20 (e.g., a nominal current) may be adjusted so that thephotodiode TIA of the light detector 22 is not saturated. The method maycontinue to a fourth step 248 in which the sensor 16 may be disposed atleast partially in a fluid and/or liquid. In a fifth step 250, the lightdetector 22 may detect a third amount of light with the light source 20off. If the third amount of light is greater than an expected amount oflight, the sensor 16 may detect a malfunction. In a sixth step 252, thelight source 20 may be turned on and the light detector 22 may detect afourth amount of light, which ECU 18 may use as and/or use to calculatea threshold amount that may be used during normal operation. Such athreshold may be used, for example and without limitation, for thresholdT₁ in connection with method 140.

With embodiments, in a seventh step 254, the ECU 18 may transition thesensor 16 to normal operation (e.g., liquid detection mode). In theliquid detection mode, the light detector 22 may detect a current amountof light, which may be compared to the threshold amount. If the currentamount of light detected is less than the threshold, the sensor 16 maydetermine that there is fluid present (step 256). If the current amountof light detected is not less than the threshold, the sensor 16 maydetermine that fluid is not present (step 258).

With embodiments, one or more of the steps of the method 140 and/or ofthe method 240 (e.g., the first through sixth steps) may be omitted,modified, and/or duplicated for certain applications. One or more stepsof the method 140 and the method 240 may be carried out, at least inpart, via the ECU 18.

Referring to FIGS. 8 and 9, embodiments of a light detector 22 aregenerally illustrated. A light detector 22 may include an optical headassembly 300 with a prism 302 and/or an optical shield 304, and anelectronic module assembly 310. The optical head assembly 300 may beconnected to the electronic module assembly 310 via one or more fiberoptic cables. A first fiber optic cable 312 (or portion of a cable) maybe connected to the optical head assembly 300 at a first end 314 andconnected to a first connector 318 at a second end 316. The first fiberoptic cable 312 may extend and/or be connected through a wall 320 of aliquid chamber 14 (e.g., a fuel tank wall), such as via a fitting 322(e.g., a hermetically sealed bulkhead fitting). A first end 332 of asecond fiber optic cable 330 may be connected with a second connector336 and a second end 334 of the second fiber optic cable 330 may beconnected with a third connector 338. The second connector 336 may beconfigured for connection with the first connector 318. The thirdconnector 338 may be configured for connection with a connector 340 ofthe electronic module assembly 310. In embodiments, such as generallyillustrated in FIG. 9, the first fiber optic cable 312 may be connectedto the optical head assembly 300 via a pair of corresponding connectors342, 344.

With embodiments, the optical head assembly 300 may be configured to bedisposed in a liquid chamber 14 (e.g., a tank) that may include volatileand/or explosive materials, such as fuel or other flammable chemicals orgases. A hermetically sealed bulkhead fitting 322 may prevent materialsfrom exiting the liquid chamber 14. While the optical head assembly 300may be disposed in a volatile environment, the electronic moduleassembly 310 may be disposed outside of the volatile environment (e.g.,outside the liquid chamber 14), and the fiber optic cable(s) (e.g.,cables 312, 330) may allow for communication between the optical headassembly 300 and the electronic module assembly 310. In suchconfigurations, passive components (e.g., the optical head assembly 300,the fitting 322, and/or fiber optic cable 312) may be the onlycomponents of the sensor 16 and/or light detector 22 disposed in thevolatile environment. Active components, such as the electronic moduleassembly 310, may be disposed outside of and/or at a safe distance fromthe volatile environment. Disposing only passive components in thevolatile environment may significantly reduce or even eliminate thepossibility of causing a spark or otherwise potentially ignitingmaterial in the volatile environment. Other designs intended to limitthe possibility of a spark/ignition may not be as effective, may be moreexpensive, and/or may be more complicated/time consuming.

With embodiments, the fiber optic cable(s) (e.g., cables 312, 330) ofthe light detector 22 may include a single fiber. The electronic moduleassembly 310 may be configured to separate incoming signals received viathe single fiber. The received signals may correspond to light received,such as from the light source 20, and may include an intensity and/or afrequency. The electronic module assembly 310 may be configured toprovide an output corresponding to the amount, intensity, and/orfrequency of light received at the optical head assembly 300. Theelectronic module assembly 310 may be connected to and/or incorporatedwith the ECU 18. Fiber optic cables, including single fiber cables, maybe relatively lightweight (e.g., about 10 times lighter) compared tocopper wiring, which may allow for greater cable lengths to be used (andfor the electronic module assembly 310 to be disposed at greaterdistances from the optical head assembly 300 and/or at more convenientlocations). Lighter cables may be particularly advantageous inapplications in which weight is a significant design factor (e.g.,airplanes). Fiber optic cables may also be smaller (e.g., in diameter)and/or more flexible than copper wiring.

Various embodiments are described herein for various apparatuses,systems, and/or methods. Numerous specific details are set forth toprovide a thorough understanding of the overall structure, function,manufacture, and use of the embodiments as described in thespecification and illustrated in the accompanying drawings. It will beunderstood by those skilled in the art, however, that the embodimentsmay be practiced without such specific details. In other instances,well-known operations, components, and elements have not been describedin detail so as not to obscure the embodiments described in thespecification. Those of ordinary skill in the art will understand thatthe embodiments described and illustrated herein are non-limitingexamples, and thus it can be appreciated that the specific structuraland functional details disclosed herein may be representative and do notnecessarily limit the scope of the embodiments.

Reference throughout the specification to “various embodiments,” “withembodiments,” “in embodiments,” or “an embodiment,” or the like, meansthat a particular feature, structure, or characteristic described inconnection with the embodiment is included in at least one embodiment.Thus, appearances of the phrases “in various embodiments,” “withembodiments,” “in embodiments,” or “an embodiment,” or the like, inplaces throughout the specification are not necessarily all referring tothe same embodiment. Furthermore, the particular features, structures,or characteristics may be combined in any suitable manner in one or moreembodiments. Thus, the particular features, structures, orcharacteristics illustrated or described in connection with oneembodiment/example may be combined, in whole or in part, with thefeatures, structures, functions, and/or characteristics of one or moreother embodiments/examples without limitation given that suchcombination is not illogical or non-functional. Moreover, manymodifications may be made to adapt a particular situation or material tothe teachings of the present disclosure without departing from the scopethereof.

It should be understood that references to a single element are notnecessarily so limited and may include one or more of such element. Anydirectional references (e.g., plus, minus, upper, lower, upward,downward, left, right, leftward, rightward, top, bottom, above, below,vertical, horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of the presentdisclosure, and do not create limitations, particularly as to theposition, orientation, or use of embodiments.

Joinder references (e.g., attached, coupled, connected, and the like)are to be construed broadly and may include intermediate members betweena connection of elements and relative movement between elements. Assuch, joinder references do not necessarily imply that two elements aredirectly connected/coupled and in fixed relation to each other. The useof “e.g.” in the specification is to be construed broadly and is used toprovide non-limiting examples of embodiments of the disclosure, and thedisclosure is not limited to such examples. Uses of “and” and “or” areto be construed broadly (e.g., to be treated as “and/or”). For exampleand without limitation, uses of “and” do not necessarily require allelements or features listed, and uses of “or” are intended to beinclusive unless such a construction would be illogical.

It is intended that all matter contained in the above description orshown in the accompanying drawings shall be interpreted as illustrativeonly and not limiting. Changes in detail or structure may be madewithout departing from the present disclosure.

What is claimed is:
 1. An electro-optic sensor, comprising: anelectronic module assembly; an optical head assembly configured to bedisposed in a liquid chamber, the optical head assembly including aright-angle prism; and a fiber optic cable configured to connect theelectronic module assembly with the optical head assembly; wherein theright-angle prism is configured to reflect residual light to a detectorwhen the right-angle prism is disposed in liquid in the liquid chamberto enable a test of the electro-optic sensor; wherein the fiber opticcable includes a first section with a first end configured forconnection to the optical head assembly and a second end configured forconnection through a wall of the liquid chamber; the fiber optic cableincludes a second section with a first end configured for connectionwith the second end of the first section; and a second end of the secondsection is configured for connection with the electronic moduleassembly.
 2. The electro-optic sensor of claim 1, including a firstconnector connected to the second end of the first section of the fiberoptic cable, and a second connector connected to the first end of thesecond section of the fiber optic cable, wherein the first connector andthe second connector are configured to be connected together.
 3. Theelectro-optic sensor of claim 2, including a third connector connectedto the second end of the second section of the fiber optic cable,wherein the electronic module assembly includes a connector configuredto be connected with the third connector.
 4. The electro-optic sensor ofclaim 1, wherein at least one of the first section and the secondsection include a single fiber.
 5. The electro-optic sensor of claim 1,including a light source configured to be driven at a plurality ofintensities, wherein the optical head assembly is configured to receivelight from the light source.
 6. A fluid system including theelectro-optic sensor of claim 1, including the liquid chamber, whereinthe optical head assembly is disposed in the liquid chamber, theelectronic module assembly is disposed outside the liquid chamber, andthe first section of the fiber optic cable is connected to the wall ofthe liquid chamber.
 7. The fluid system of claim 6, wherein the firstsection of the fiber optic cable is connected to the wall via ahermetically sealed fitting.
 8. The fluid system of claim 7, wherein allactive components of the electro-optic sensor are disposed outside ofthe liquid chamber.
 9. The fluid system of claim 6, wherein the firstend of the first section of the fiber optic cable is connected to theoptical head assembly via corresponding connectors.
 10. Theelectro-optic sensor of claim 1, wherein the right-angle prism isoptically transmissive.
 11. The electro-optic sensor of claim 1, whereinthe optical head assembly includes a reflective optical member.
 12. Theelectro-optic sensor of claim 1, wherein the optical head assemblyincludes a light source; and the right-angle prism is disposed at leastpartially between the light source and the reflective optical member.13. The electro-optic sensor of claim 1, wherein the optical headassembly includes a light source configured to provide light at aplurality of intensities for assessing an operational state of theelectro-optic sensor.